Lyric discussion by montresor 

Surely this song is about the paradox of having made it and being on top and still feeling like crap and having the same negative self-image and even greater self-doubt as when he was nothing. The self-image problem makes the jump to the drug abuse references easy.
Think about how optimistic the music and the initial lyrics of Major Tom are. Sure, ours is a dystopian universe - the people who have the stage can't even change the world (planet earth is blue and there is nothing I can do) or really even save themselves by returning to earth (Can you hear me Major Tom) once they've made it out of the stratosphere (superstardom, that is). But, then to discover there is no such thing as happiness (I am happy, hope you're happy too) or love (sordid details to follow) only the shrieking of nothing our own inner voice which in Bowie's case was pretty low during much of the 70's. That's how you get "Strung out in heaven's high"(that is on top of the world) "hitting an all time low" (ironic, isn't it, dope addicted and suicidal for all that money and fame).

@montresor This is the best interpretation of the song. It is about celebrity culture and isolation. Messing with Major Tom sounds more like forgetting who you really are, and losing all happiness and sense of direction. Becoming overtaken by one's own ego.

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